1. Field of the Invention
This invention relates to a polyolefin composition which is remarkably improved in its adhesiveness to a wide variety of substrates, in particular, to metals, and a process for preparing such polyolefin composition.
2. Description of the Prior Art
Polyolefins, for example, polyethylene, polypropylene, etc. are known to have various excellent properties and are presently used in a wide variety of applications. However, polyolefins possess disadvantages in that the adhesion of polyolefins to metals or other substrates is very difficult because of their non-polarity. In particular, the adhesion is found to be more difficult in highly crystalline polyolefins or in polyolefins which tend to form a layer having a mechanically weak adhesive strength on the surface of the articles, and their utilities are thus remarkably limited. In order to eliminate the above disadvantage various procedures have been proposed, including pre-treatment of the bonding surface of polyolefins with acids, flame, corona discharge, etc., and the use of a primer such as an ethylene-acrylic acid copolymer between the surfaces of the substrate and the polyolefin to be bonded. Also, it is known that the adhesive strength can be improved by blending a polyolefin with a specific polymer having good adhesiveness to the substrates to be bonded or by copolymerizing an olefin and a comonomer which contains functional groups having adhesiveness to the substrates to be bonded, or the like. However, these known procedures are still not satisfactory in practical use because they sometimes do not provide a sufficient adhesive strength, or, in some cases, they adversely affect the advantageous properties of the polyolefins, or they are not economically advantageous.